Structures and methods for high-efficiency pyramidal three-dimensional solar cells

Abstract

The present disclosure enables high-volume cost effective production of three-dimensional thin film solar cell (3-D TFSC) substrates. Pyramid-like unit cell structures 16 and 50 enable epitaxial growth through an open pyramidal structure 3-D TFSC embodiments 70, 82, 100 , and 110 may be combined as necessary. A basic 3-D TFSC having a substrate, emitter, oxidation on the emitter, and front and back metal contacts allows for simple processing. Other embodiments disclose a selective emitter, selective backside metal contacts, and front-side SiN ARC layers. Several processing methods, including process flows 150, 200, 250, 300 , and 350 , enable production of these 3-D TFSCs.

What is claimed is: 
     
       1. A pyramidal three-dimensional thin film solar cell (3-D TFSC) having enhanced processing properties, comprising:
 an n-type epitaxial 3-D TFSC substrate comprising a plurality of pyramidal unit cells, wherein said unit cells comprise:
 tapered sidewalls having different crystallographic planes including the <111> plane, said tapered sidewalls forming an open pyramid-like structure; 
 a substantially flat top-ridge having a crystallographic <100> plane, said top-ridge associated with said tapered sidewalls; and 
 said tapered sidewalls having a backside surface; and 
 
 said 3-D TFSC substrate further comprising a back n+ doped layer; 
 a single p-type dopant diffusion emitter layer formed in said tapered sidewalls and said top-ridge; 
 an oxide passivation layer formed on said emitter layer, said oxide passivation layer formed on said tapered sidewalls; 
 a blanket metal contact layer formed on said back surface; and 
 front metal contacts formed on said emitter layer, said front metal contacts formed on said top-ridge. 
 
     
     
       2. The 3-D TFSC of  claim 1  wherein said n+ doped layer further comprises in-situ doped n+ layer. 
     
     
       3. The 3-D TFSC substrate of  claim 1 , wherein said n-type epitaxial substrate doping is varied. 
     
     
       4. The 3-D TFSC substrate of  claim 1 , wherein said n type epitaxial substrate doping is constant. 
     
     
       5. The 3-D TFSC substrate of  claim 1 , further comprising a silicon substrate. 
     
     
       6. The 3D TFSC substrate of  claim 1 , wherein the p+ dopant layer comprises an in-situ emitter. 
     
     
       7. A pyramidal three-dimensional thin film solar cell (3-D TFSC) having enhanced processing properties, comprising:
 an n-type epitaxial 3-D TFSC substrate comprising a plurality of pyramidal unit cells, wherein said unit cells comprise:
 tapered sidewalls having a crystallographic <111> plane, said tapered sidewalls forming an open pyramid-like structure; 
 a substantially flat top-ridge having a crystallographic <100> plane, said top-ridge associated with said tapered sidewalls; and 
 said tapered sidewalls having a back surface; and 
 
 said 3-D TFSC substrate further comprising a back n+ doped layer; 
 a p-type dopant diffusion emitter layer formed in said tapered sidewalls; 
 a p-type dopant diffusion selective emitter layer formed in said top-ridge; 
 an oxide passivation layer formed on said emitter layer, said oxide passivation layer formed on said tapered sidewalls; 
 a blanket metal contact layer formed on said backside surface; and 
 front metal contacts formed on said emitter layer, said front metal contacts formed on said top-ridge. 
 
     
     
       8. The 3-D TFSC substrate of  claim 7 , wherein said selective emitter layer is doped less heavily than said emitter layer. 
     
     
       9. The 3-D TFSC substrate of  claim 7 , wherein said n+ doped layer is in-situ doped. 
     
     
       10. The 3-D TFSC substrate of  claim 7 , wherein said p type n-type epitaxial substrate doping is varied. 
     
     
       11. The 3-D TFSC substrate of  claim 7 , wherein said p typo n-type epitaxial substrate doping is constant. 
     
     
       12. The 3-D TFSC substrate of  claim 7 , further comprising a silicon substrate. 
     
     
       13. The 3-D TFSC substrate of  claim 7 , further comprising a SiN ARC layer formed on said oxide passivation layer. 
     
     
       14. A pyramidal three-dimensional thin film solar cell (3-D TFSC) having enhanced processing properties, comprising:
 an n-type epitaxial 3-D TFSC substrate comprising a plurality of pyramidal unit cells, wherein said unit cells comprise:
 tapered sidewalls having a crystallographic <111> plane, said tapered sidewalls forming an open pyramid-like structure; 
 a substantially flat top-ridge having a crystallographic <100> plane, said top-ridge associated with said tapered sidewalls; and 
 said tapered sidewalls having a backside surface; and 
 
 said 3-D TFSC substrate further comprising a back n+ doped layer; 
 a p-type dopant diffusion emitter layer formed in said tapered sidewalls and said top-ridge; 
 an oxide passivation layer formed on said emitter layer, said oxide passivation layer formed on said tapered sidewalls; 
 a complete passivation layer formed at least partially on said backside surface; 
 a selective metal contact layer formed on said complete passivation layer on said back surface, said selective metal contact at least partially contacting said n-type epitaxial 3-D TFSC; and 
 front metal contacts formed on said emitter layer, said front metal contacts formed on said top-ridge. 
 
     
     
       15. The 3-D TFSC substrate of  claim 14 , wherein said emitter layer further comprises a selective emitter layer formed in said top-ridge. 
     
     
       16. The 3-D TFSC substrate of  claim 15 , wherein said selective emitter layer is doped less heavily than said emitter layer. 
     
     
       17. The 3-D TFSC substrate of  claim 14 , wherein said n+ doped layer further comprises an in-situ doped n+ layer. 
     
     
       18. The 3-D TFSC substrate of  claim 14 , wherein said n-type epitaxial substrate doping is varied. 
     
     
       19. The 3-D TFSC substrate of  claim 14 , wherein said n-type epitaxial substrate doping is constant. 
     
     
       20. The 3-D TFSC substrate of  claim 14 , further comprising a silicon substrate. 
     
     
       21. The 3-D TFSC substrate of  claim 14 , further comprising a SiN ARC layer formed on said oxide passivation layer.